Seasonal and geographic variation in the diet of Barn Owls (Tyto alba) in temperate agroecosystems of Argentina.

GONZÁLEZ-FISHER, C.; CODESIDO, M.; TETA, P.; BILENCA, D. N.

ORNITOLOGIA NEOTROPICAL

NEOTROPICAL ORNITHOLOGICAL SOC

Año: 2011 vol. 22 p. 295 - 305

1075-4377

We studied the dietary niche of Barn Owl (Tyto alba) in temperate agroecosystems of central Argentina by describing seasonal and geographic variation in the food habits of this owl in four districts of the Pampean region (Flooding, Inland, Rolling, and Southern Pampas). We identified 20,113 prey items from samples of fresh pellets collected in summer (n = 23) and winter (n = 26). Mammals, mostly sigmodontine rodents, were the main prey items (91.7%), followed by amphibians (6.7%) and birds (1.6%). Arthropods were also a common prey item (found in 45% of the samples). The consumption of arthropods and amphibians was higher in summer than in winter, indicating that seasonal changes in prey abundances are reflected in the Barn Owl diet. We found no differences in food-niche breadth among the four study districts, but food-niche breadth varied between seasons, being higher during summer. Six rodent species were common to all districts: Calomys spp., Akodon azarae, Oligoryzomys flavescens, Mus musculus, Rattus spp., and Holochilus brasiliensis. Calomys spp. was numerically dominant in 46 of the 49 samples, and together with A. azarae and O. flavescens comprised the bulk of the diet (>80%). Predation on rodents may reflect population dynamics of the prey species with high predation rates when peaks in abundance of sigmodontine rodents occurred (autumn-winter).